The invention generally pertains to projection display systems and more particularly to a new color projection display system using one or more self emitting display panels.
Existing projection display systems typically comprise a light source, one or more display panels that modulate the light from the light source, and a projection lens that collects the modulated light and projects it to the screen. The display panel typically employs a liquid crystal display (“LCD”) or Micro-electromechanical Systems (“mems”) device. There are several problems with the existing technology. For example, the illumination system including the light source is complex in structure, expensive, and bulky. Typically, it needs several relay lenses, light pipe and other optical components. In addition, the light efficiency of the projection system is low. In the pixels of a display that is in the on-state, the light is directed to the screen to generate pictures. In the pixels of an off-state display, the light is either absorbed or deflected away from the screen to generate a dark picture. Though the picture is dark, it requires the same amount of energy as a bright picture. The light energy is wasted in the pixels of an off-state display.
U.S. Pat. No. 6,573,579 discloses a projector based on Organic Light-Emitting Diode (“OLED”) panels, which is one type of emissive display. But the disclosed projector has a problem that cannot be solved. If the emitters generate red, green, and blue (“RGB”) colors directly, existing manufacturing processes cannot make RGB emitters with ultra fine pitch. This is because the moisture in processing of pixelization reduces the life time of OLED panels, so the resolution is too low for a projection system. If the emitters generate RGB through a color filter, ⅔ of the light is cut off. Therefore the light efficiency is too low.
U.S. Pat. No. 6,939,012B discloses a laser projector that uses an OLED pixel to pump another organic cavity. The cavity length of a laser depends on its emitting color. Different colors require different cavity lengths. It is very hard to manufacture these OLED pixels and cavities in a micro display where the size of pixels is very small.
As a result, there exists a current need for a simple, low cost and compact projection system with viable manufacturability for high resolution display.